Surface treatment method for plate material, and radiating fin for heat exchanger

ABSTRACT

The present invention reduces the expense of treating the surfaces of a plate material. This surface treatment method treats the surfaces of a plate material that is rolled with rolling oil and employed as a cooling fin of a heat exchanger, and includes a preparation step and a coating application step. In the preparation step, the plate material is prepared. In the coating application step, a coating is applied to the surface of the plate material without carrying out a degreasing treatment.

TECHNICAL FIELD

The present invention relates to a method of treating the surface of aplate material, and more specifically relates to a method of treatingthe surface of a plate material in which the plate material is rolledwith rolling oil, the plate material being employed as cooling fins forheat exchangers.

In addition, the present invention relates to cooling fins for heatexchangers, and in particular relates to plate-shaped fins disposedinside a heat exchanger formed from a plate material that is rolled withrolling oil.

BACKGROUND ART

The outdoor unit and indoor unit of an air conditioner each generallyinclude a heat exchanger for exchanging heat between the heat exchangerand the air surrounding it. A heat exchanger normally includes aplurality of cooling fins, a plurality of heat transfer lines, and airtransport means such as a propeller fan or the like. The plurality ofcooling fins are plate-shaped members that are disposed with apredetermined gap between each member in the plate thickness direction.The plurality of heat transfer lines are mounted such that they passthrough the plurality of cooling fins in the plate thickness direction.The air transport means serves to transport an air flow to the pluralityof cooling fins and heat transfer lines.

In this heat exchanger, heat exchange occurs by transporting an air flowwith the air transport means through the gaps between adjacent coolingfins, and evaporating or condensing refrigerant that flows inside theheat transfer lines.

The cooling fins are generally composed of a pure aluminum platematerial, and the plate material is manufactured by cutting the platematerial into predetermined fin shapes by means of a metal die. Beforethe plate material is cut, a corrosion resistant coating is applied tothe plate material to form a corrosion resistant film that will improvethe corrosion resistance of the plate material.

However, rolling oil remains on the surface of the plate materialbecause rolling oil is used to roll and manufacture the plate material.Because of this, when the coating is applied to the surface of the platematerial, the coating will be repelled by the rolling oil and thus itwill be difficult to apply the coating. Accordingly, in a conventionalsurface treatment, before the coating is applied, the plate material isdipped in a tank of alkaline solution in order to degrease the platematerial, and is then dipped in a tank of a chromic acid processingagent in order to both form the corrosion resistant film on the surfacethereof and roughen the surface thereof.

This conventional method of treating the surfaces of the plate materialis quite expensive because of the need for processing tanks for thedegreasing and chromic acid processes.

In addition, because the treatment waste fluid produced by the chromicacid process includes heavy metals and is a problem from anenvironmental point of view, it will be necessary to dispose of thetreatment waste fluid after a predetermined number of treatments.However, when this waste fluid is processed, the running cost thereof isquite expensive because specialized waste fluid tanks must be treateddifferently, and because the waste fluid must be processed at fixedintervals of time.

DISCLOSURE OF THE INVENTION

An object of the present invention is to reduce the expense of treatingthe surfaces of plate material. In addition, another object of thepresent invention is to carry out this type of surface treatment toobtain cooling fins for heat exchangers.

A surface treatment method according to claim 1 is a method for treatingthe surface of a plate material that is rolled with rolling oil andemployed as cooling fins for heat exchangers, the method including afirst step and a second step. In the first step, the plate material isprepared. In the second step, a coating is applied to the surfaces ofthe plate material without carrying out a degreasing treatment.

In this method, a coating can be applied to a plate material withoutperforming a degreasing treatment, and thus a conventional degreasingtreatment tank will not be necessary and costs will be reduced.

The surface treatment method according to claim 2 is the surfacetreatment method of claim 1, in which in the second step the coating isapplied to the surface of the plate material without carrying out asurface roughing treatment.

In this method, a coating can be applied to a plate material withoutperforming a surface roughing treatment, and thus a conventional chromicacid treatment tank will not be necessary and costs will be reduced. Inaddition, running costs can be avoided because waste fluid treatmentneed not be performed.

The surface treatment method according to claim 3 is the surfacetreatment method of claim 1 or 2, in which in the second step thecoating is applied to the surface of the plate material by transportingthe plate material at a speed of 50 m/min or less.

In this method, the coating having a high viscosity and not easilyrepelled by oil can be employed because the coating is applied to theplate material at a comparatively slow speed. Thus by adopting thismethod, a degreasing treatment can be omitted.

A surface treatment method according to claim 4 is the surface treatmentmethod of claim 3, in which the coating has a viscosity that is relatedto the application speed at which the coating is applied to the platematerial.

When the speed at which the coating is applied changes, the viscosity ofthe coating that can be used at that application speed will also change.Here, the viscosity of the coating that can be used is related to thespeed at which the coating is applied.

A surface treatment method according to claim 5 is the surface treatmentmethod of any of claims 1 to 4, in which in the second step the coatingis dried in atmospheric air at a temperature between 240° C. and 270° C.

In this method, rolling oil remaining on the plate material will beeasily dissolved in the coating because the coating is dried inatmospheric air at a comparatively high temperature. Thus, even if adegreasing treatment is omitted, a coating film can be stably formed onthe surface of the plate material.

A surface treatment method according to claim 6 is the surface treatmentmethod of any of claims 1 to 5, in which the coating includes acorrosion resistant coating and a hydrophilic coating. In addition, thesecond step includes a third step and a fourth step. In the third step,the corrosion resistant coating is applied to the surface of the platematerial. In the fourth step, the hydrophilic coating is applied to thesurface of the plate material after the third step.

When the cooling fins are, for example, employed in a heat exchanger ofan indoor unit, they will be required to have hydrophilic properties inaddition to a resistance to corrosion. In this situation, after acorrosion resistant film is formed on the surface of the plate material,a hydrophilic film will be formed on top of the corrosion resistantfilm.

Here, this method is primarily directed at a surface treatment for aplate materials employed as cooling fins in an heat exchanger for anoutdoor unit.

A surface treatment method according to claim 7 is the surface treatmentmethod of any of claims 1 to 6, in which in the fourth step the platematerial is transported in a transport path that is the same as thetransport path of the third step but in a direction that is opposite tothat of the third step.

The plate material is normally transported at a predetermined speed andcoatings are applied thereto and dried. However, in this method, boththe corrosion resistant coating and the hydrophilic coating are appliedin the same path, and thus both drying steps can be performed byarranging, for example, only one drying oven in the transport path.Because of this, costs can be further reduced, and work efficiency canbe improved.

The surface treatment method according to claim 8 is the surfacetreatment method of claim 7, in which in the third step the coating isapplied to the plate material in atmospheric air that is at atemperature that is lower than that of the fourth step.

In this method, the corrosion resistant coating is applied at atemperature that is lower than the temperature at which the hydrophiliccoating is applied, and thus the production of heat history in thecorrosion resistant coating can be avoided when the hydrophilic coatingis dried.

A cooling fin for a heat exchanger according to claim 9 is composed of aplate material that was rolled with a rolling oil, and having a plateshape for radiating heat that is disposed inside the heat exchanger. Thecooling fin includes a fin unit and a coating film. The coating film isformed on the surfaces of the fin unit. 10 mg or less of the rolling oilare included per 1 m² of the surface of the fin unit.

The cooling fins have a predetermined amount of rolling oil remainingthereon, which can confirm that the surface treatment did not include adegreasing treatment.

A cooling fin for a heat exchanger according to claim 10 is composed ofa plate material that was rolled with a rolling oil, and having a plateshape for radiating heat that is disposed inside the heat exchanger. Thecooling fin includes a fin unit and a coating film. The coating film isformed on the surfaces of the fin unit. And, the coating film has a peakin the infrared spectrum that corresponds to the primary constituent ofthe rolling oil.

The cooling fin has a portion of the rolling oil remaining thereon inthe dissolved state, and thus when the infrared spectrum of the coatingfilm is measured, a peak that corresponds to the primary constituent ofthe rolling oil will appear. Thus, it can be confirmed that the surfaceof the cooling fin was treated without a degreasing treatment.

A cooling fin for a heat exchanger according to claim 11 is the coolingfin for a heat exchanger of claim 10, in which the coating film has apeak in the infrared spectrum in a range between 1500 cm⁻¹ and 2000cm⁻¹.

A cooling fin having a coating film with a peak in the infrared spectrumin this range is sought because there are many commonly used rollingoils that have a peak in this range.

This cooling fin has a portion of the rolling oil remaining thereon inthe dissolved state, and thus when the infrared spectrum of the coatingfilm is measured, a peak that corresponds to the primary constituent ofthe rolling oil will appear. Thus, it can be confirmed that the surfaceof the cooling fin was treated without a degreasing treatment.

A cooling fin for a heat exchanger according to claim 12 is the coolingfin for a heat exchanger of any of claims 9 to 11, in which there areconcave and convex portions on the surface of the coating film in arange between 2 and 5 micrometers in the plate thickness direction.

The cooling fin has not had a surface roughing treatment carried out onit, and thus the concave and convex portions on the surface of thecoating film are smaller than those produced by a surface roughingtreatment, and the convex and concave portions are maintained within theaforementioned range. Thus, it can be confirmed that the surface of thecooling fin was treated without a surface roughing treatment.

A cooling fin for a heat exchanger according to claim 13 employs a platematerial treated by means of a surface treatment method disclosed in anyof claims 1 to 8.

This cooling fin is manufactured by employing a plate material treatedby the aforementioned surface treatment method, and was manufactured viaa treatment process that reduces the cost of equipment or the like forsurface treatment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a summary of a method of treating the surfaces of a platematerial according to an embodiment of the present invention.

FIG. 2 is a graph showing the relationship between the speed at whichthe coating used in the aforementioned surface treatment method isapplied and the viscosity of the coating.

FIG. 3 is a plan view showing a cooling fin for a heat exchangeraccording to an embodiment of the present invention.

FIG. 4 is a longitudinal cross-section of the aforementioned coolingfin.

BEST MODE FOR CARRYING OUT THE INVENTION

[Method of Treating the Surfaces of a Plate Material]

FIG. 1 shows a summary of a surface treatment method according to anembodiment of the present invention.

First, the device that is employed in this surface treatment method willbe described.

A plate material 1 is set such that it extends between two coilers 21,31. The coilers 21, 31 are devices which can respectively unroll andwind up the plate material 1, and the plate material 1 can betransported to either left or right in FIG. 1 by either unrolling theplate material 1 or by winding up the plate material 1.

A drying oven 23 is disposed approximately midway between the twocoilers 21, 31, and serves to dry a coating applied to the surfaces ofthe plate material 1. The drying oven 23 is open in the direction inwhich the plate material 1 is transported, and the plate material 1 ismovably disposed inside the drying oven 23.

A roll coater 25 for applying a corrosion resistant coating (describedbelow) is disposed on the coiler 21 side of the drying oven 23, and aroll coater 35 for applying a hydrophilic coating (described below) isdisposed on the coiler 31 side of the drying oven 23. The roll surfaceof the roll coater 25 is mesh finished in order to increase theretentivity of the coating, and the roll surface of the roll coater 35is dull-finished.

In addition, processing units 27, 37 for affixing a processing agent tothe surface of the coating are respectively disposed on the downstreamside in the transport direction of the roll coaters 25, 35, and coolingblowers 29, 39 for cooling the plate material 1 heated by the dryingoven 23 are disposed further downstream from the drying oven 23.

Next, the surface treatment method will be described.

This method serves to treat the surface of a plate material 1 that wasrolled with rolling oil. The plate material 1 is employed primarily forcooling fins that are disposed inside heat exchangers for the indoor andoutdoor units of an air conditioner.

This method includes a preparation step and a coating application step.

In the preparation step, a plate material 1 that is wound into a roll isprepared, and set onto the coilers 21, 31. The plate material 1 is madefrom pure aluminum, and is manufactured by rolling with a rolling oil.

In the coating application step, a coating is applied to the surfaces ofthe plate material 1 without carrying out a degreasing treatment and asurface roughing treatment. This step includes a corrosion resistantcoating application step and a hydrophilic coating application step.

In the corrosion resistant coating application step, a corrosionresistant coating is applied to the surfaces of the plate material 1 bymeans of the roll coater 25. In this step, the coating is applied at afixed speed by means of the roll coater 25 by transporting the platematerial 1 to the right in FIG. 1 at a fixed speed. Here, the coating isapplied at a speed of 50 m/min or less, and preferably at a speed of 10to 40 m/min.

An epoxy resin coating is employed as the corrosion resistant coating.The viscosity of the coating that can be employed here is related to thespeed at which the coating is applied to the plate material 1. Morespecifically, a coating is used which has a viscosity in a rangerepresented by the diagonal lines in FIG. 2. Note that when theapplication speed is high, a coating with a low viscosity cannot be usedin the present method. This is because when the viscosity is low, thecoating cannot be satisfactorily retained on the rollers of the rollcoater 25, and thus cannot be satisfactorily applied to the platematerial 1. Thus, for example, when the application speed is 50 m/min,it is preferable to use a coating having a viscosity of 40 sec orhigher. Note that in conventional surface treatments, the coating isapplied at a speed of between 100 and 250 m/min.

In addition, after the coating application, the plate material 1 istransported to the drying oven 23, and dried in atmospheric air at atemperature between 240 and 270° C. Here, the plate material 1 is driedat a temperature that is lower than the drying temperature used in thesubsequent hydrophilic coating application step.

In the hydrophilic coating application step, a hydrophilic coating isapplied to the surfaces of the plate material 1 by means of the rollcoater 35. In this step, the coating is applied at a fixed speed bytransporting the plate material 1 to the left in FIG. 1 at a fixedspeed. The application speed is identical to that at which the corrosionresistant coating was applied.

An acrylic resin coating is employed as the hydrophilic coating. Theviscosity of the hydrophilic coating that can be employed here isrelated to the application speed in the same way as that of thecorrosion resistant coating. In addition, in this step, the hydrophiliccoating is dried in the same atmospheric air where the corrosionresistant coating was dried, however as noted above, the temperature atwhich the hydrophilic coating is dried is higher than the temperature atwhich the corrosion resistant coating is dried.

In this surface treatment method, the plate material 1 is firsttransported from the coiler 21 toward the coiler 31. Next, the platematerial 1 has a corrosion resistant coating applied thereto by means ofthe roll coater 25 without carrying out a degreasing treatment and achromic acid treatment. Then, after a processing agent is affixed to theplate material 1 by the processing unit 27, the plate material 1 isheated up to the aforementioned predetermined temperature inside thedrying oven 23, and the coating is dried and hardened. After that, theplate material 1 is cooled by the cooling blower 29 and wound by thecoiler 31.

Next, the plate material 1 is transported from the coiler 31 toward thecoiler 21, while the hydrophilic coating is applied by the roll coater35. Then, after a processing agent is affixed to the plate material 1 bythe processing unit 37, the plate material 1 is heated up to theaforementioned predetermined temperature inside the drying oven 23, andthe coating is dried and hardened. After that, the plate material 1 iscooled by the cooling blower 39 and wound by the coiler 21.

According to this surface treatment method, the coating is applied tothe plate material 1 at a speed that is comparatively slower than theconventional speed, and thus a coating having a comparatively highviscosity can be employed. Because of this, even if rolling oil remainson the plate material 1, a coating can be prevented from being repelledby the rolling oil and a coating film can be formed. Then, by applyingthis method, a conventional degreasing treatment and surface roughingtreatment can be omitted, and thus a treatment layer for each treatmentwill not be necessary and costs will be greatly reduced.

In addition, in this method, there will be no need to treat waste fluidand the running costs for surface treatment will be avoided because thechromic acid treatment can be omitted.

[Cooling Fins for a Heat Exchanger]

FIGS. 3 and 4 show a cooling fin 11 for a heat exchanger which isemployed in an embodiment of the present invention.

The cooling fin 11 is a plate-shaped fin for radiating heat that isdisposed inside a heat exchanger. The cooling fin 11 is composed of theplate material 1 that has been treated by means of the aforementionedsurface treatment method, and includes a fin unit 13 and a coating film15.

The fin unit 13 is manufactured by cutting the plate material 1 into apredetermined fin shape by means of a metal die, and forming it into theshape shown in the figures. In addition, the fin unit 13 includes aplurality of holes 13 a in which a plurality of heat transfer lines (notshown in the figures) that are disposed inside the heat exchanger passthrough the holes 13 a.

The coating film 15 is formed on the surfaces of the fin unit 13. Thecoating film 15 includes 10 mg or less of a rolling oil per each 1 m² ofthe surface of the fin unit 13. In addition, the coating film 15 has apeak in the infrared spectrum in a range between 1500 cm⁻¹ and 2000cm⁻¹. Furthermore, the surface of the coating film 15 has convex andconcave portions thereon whose heights and depths in the plate thicknessdirection are in a range between 2 and 5 micrometers when measured by ascanning electron microscope (SEM).

The cooling fin 11 obtained by the aforementioned surface treatmentincludes a predetermined amount of rolling oil because a degreasingtreatment is not carried out. In addition, when the infrared spectrumwas measured, it was confirmed that a degreasing treatment was notperformed because a peak appeared that showed the presence of rollingoil. Furthermore, when the concave and convex portions on the surface ofthe coating film 15 were measured by a scanning electron microscope, itwas confirmed that a chromic acid treatment was not performed becausethe concave and convex portions were in a range that were comparativelysmaller than when a surface treatment that includes a chromic acidtreatment was performed.

In addition, the cooling fin 11 is primarily used as a cooling fin for aheat exchanger for an indoor unit because a hydrophilic coating isformed on the surface thereof.

Other Embodiments

(a) The aforementioned surface treatment method may be employed in asurface treatment of a plate material for manufacturing cooling finsemployed in a heat exchanger for devices other than outdoor and indoorunits of an air conditioner.

(b) The aforementioned surface treatment method may only include theapplication of a corrosion resistant coating to the plate material.Here, this plate material can be used primarily for cooling fins for aheat exchanger of an outdoor unit.

(c) The aforementioned surface treatment method may employ a coatingthat affixes a predetermined coloring agent. Here, the film thickness ofa coating film can be visually confirmed by the degree of color(lightness and darkness) because the portions of the coating film thatare not repelled by the rolling oil will be colored and visible.

INDUSTRIAL APPLICABILITY

According to the present invention, a coating can be applied to a platematerial without performing a degreasing treatment, and thus aconventional degreasing treatment tank will not be necessary and costsfor equipment will be reduced.

1. A method of treating a surface of a plate material that is rolledwith rolling oil, the method comprising the steps of: a first step inwhich the plate material is prepared; and a second step in which acoating is applied to the surface of the plate material without carryingout a degreasing treatment.
 2. The method of treating the surface of theplate material set forth in claim 1, wherein in the second step thecoating is applied to the surface of the plate material without carryingout a surface roughing treatment.
 3. The method of treating the surfaceof the plate material set forth in claim 1, wherein in the second stepthe coating is applied by transporting the plate material at a speed of50 m/min or less.
 4. The method of treating the surface of the platematerial set forth in claim 3, wherein the coating has a viscosity thatis related to the application speed at which the coating is applied tothe plate material.
 5. The method of treating the surface of the platematerial set forth in claim 1, wherein in the second step the coating isdried in atmospheric air at a temperature between 240 and 270° C.
 6. Themethod of treating the surface of the plate material set forth in claim1, wherein the coating includes a corrosion resistant coating and ahydrophilic coating, and the second step includes a third step in whichthe corrosion resistant coating is applied to the surface of the platematerial and a fourth step in which the hydrophilic coating is appliedto the surface of the plate material after the third step.
 7. The methodof treating the surface of the plate material set forth in claim 6,wherein in the fourth step the plate material is transported in atransport path that is the same as the transport path of the third stepbut in a direction that is opposite to that of the third step.
 8. Themethod of treating the surface of the plate material set forth in claim7, wherein in the third step the coating is applied to the platematerial in atmospheric air whose temperature is lower than that in thefourth step.
 9. A fin (11) composed of a plate material that was rolledwith a rolling oil and having a plate shape, comprising: a fin unit; anda coating film that is formed on the surface of the fin unit; wherein 10mg or less of the rolling oil is included per 1 m² of the surface of thefin unit.
 10. A fin (11) composed of a plate material that was rolledwith a rolling oil and having a plate shape, comprising: a fin unit; anda coating film that is formed on the surface of the fin unit; whereinthe coating film has a peak in the infrared spectrum that corresponds tothe primary constituent of the rolling oil.
 11. The fin (11) set forthin claim 10, wherein the coating film has a peak in the infraredspectrum in a range between 1500 cm⁻¹ and 2000 cm⁻¹.
 12. The fin (11)set forth in claim 9, wherein concave and convex portions in the platethickness direction on the surface of the coating film are in a rangebetween 2 and 5 micrometers.
 13. A fin (11) that employs a platematerial treated by means of a surface treatment method disclosed inclaim
 1. 14. The fin set forth in claim 9 for radiating heat that isdisposed inside a heat exchanger.
 15. The fin set forth in claim 9,wherein the plate material is made from pure aluminum.
 16. A platemember that is treated by means of the surface treatment methoddisclosed in claim
 1. 17. The method of treating the surface of theplate material set forth in claim 7, wherein the plate material isemployed as cooling fins for heat exchangers.
 18. The method of treatingthe surface of the plate material set forth in claim 1, wherein theplate material is made from pure aluminum.
 19. The fin set forth inclaim 10, wherein concave and convex portions in the plate thicknessdirection on the surface of the coating film are in a range between 2and 5 micrometers.
 20. The fin set forth in claim 10 for radiating heatthat is disposed inside a heat exchanger.
 21. The fin set forth in claim10, wherein the plate material is made from pure aluminum.